Structural features of uranyl acrylate complexes with s-, p-, and d-monovalent metals

A series of uranyl acrylate complexes with s-, p-, and d- monovalent cations (Li, Na, Tl, and Ag) was synthesized and characterized by single crystal X-ray diffraction and IR spectroscopy. We demonstrated that the nature of the monovalent cation strongly affects the composition and crystal structure of an uranyl acrylate. Li[UO2(acr)3]·H2O (1, acr=CH2CHCOO−) crystallizes in the tetragonal crystal system and is built of chains which are connected through hydrogen bonding. The presence of an acrylic acid dimer in the reaction results in the monoclinic compound Na3[UO2(acr)3][UO2(acr)2.5(CH2CHCOOCH2CH2COO)0.5]2·5H2O (2), in which the acrylic dimer shares a position with both the acrylate anion and a water molecule. Tl[UO2(acr)3] (3) exists as two polymorphs and crystallizes in either P1̅ (3a) or P213 (3b) space groups. The polymorphs differ in the dimensionality, 2D for 3a and 3D for 3b, and density. Ag2[UO2(NO3)2(acr)2]·2Hacr (4) is the first example of the Ag atom coordination to the acrylate anion through the vinyl group. In 4, the Ag–C bonds enhances the connectivity of the trinuclear [Ag2UO2(acr)2(Hacr)2(NO3)2] clusters into a layered coordination polymer. A detailed structural study of the obtained compounds was performed using Voronoi-Dirichlet tessellation.

A new ternary compound with the BGa8Ir4 structure type in the Al–Au–Ir system

Following the recent determination of the Al3AuIr structure, a new ternary phase has been identified in the Al–Au–Ir phase diagram. It has a chemical composition Al9(Au;Ir)4 with an apparently low gold content. Its crystal structure has been determined with single-crystal X-ray diffraction. The new compound crystallizes in the tetragonal crystal system and has been successfully solved in space group I41/acd (Pearson symbol tI104) with lattice parameters a = 8.6339 (2) and c = 21.8874 (7) Å. Atomic environments are described as well as similarities with the BGa8Ir4 compound.

Synthesis and structural characterization of Ca12Ge17B8O58

Ca12Ge17B8O58 was prepared by high-temperature solid state synthesis at 1100°C in a platinum crucible from calcium carbonate, boric acid, and germanium(IV) oxide. The compound crystallizes in the tetragonal crystal system in the space group P4̅ (No. 81) isotypically to Cd12Ge17B8O58. The structure was refined from single-crystal X-ray diffraction data: a = 15.053(8), c = 4.723(2) Å, V = 1070.2(2) Å3, R1 = 0.0151, and wR2 = 0.0339 for all data. The crystal structure of Ca12Ge17B8O58 consists of [Ge4O12]n chains composed of GeO4 tetrahedra and GeO6 octahedra. The chains are interconnected into a [Ge4O10.5]n network via corner sharing. By additional [Ge(B2O7)4]28– clusters, these units are connected to a three-dimensional [Ge17B8O58]24– framework. The open structure forms three types of tunnels with five-, six-, and seven-membered rings (MRs) along the c axis, where the Ca2+ are located.

Hydrothermal Synthesis and Multicolor Upconversion Fluorescence of Novel LiLuF4:Yb3+, Tm3+ Microcrystals

LiLuF4:Yb3+, Tm3+ upconversion luminescence materials were synthesized by a hydrothermal method, in which NaF and NaBF4 were used as fluorine sources (labeled as sample A and B, respectively). Their morphologies, XRD patterns and UC emission properties were compared. The synthesized crystallites consist of regular octahedrons of several micrometers and aggregates. The XRD patterns indicate that they belong to tetragonal crystal system with I41/a space group. These microcrystals emit strong UC violet, visible and near infrared light under the excitation of 980 nm laser diode. The multicolor UC emissions from sample B are much stronger than those from sample A. The strong emission intensity is ascribed to good crystal quality of sample B.

Stereospecific ligands and their complexes - Part XIV: Crystal structure of O,O’-dipropyl ester of (S,S)-ethylenediamine-N,N’-di-2-(4-methyl)-pentanoic acid dihydrochloride

Bidentate N,N'-ligand precursor, O,O'-dipropyl ester of (S,S)- ethylenediamine-N,N'-di-2-(4-methyl)-pentanoic acid dihydrochloride, [(S,S)- H4eddl]Cl2, was prepared and its crystal structure is given herein. It crystallizes in a P42 space group of tetragonal crystal system with a = 16.5620 (2) ?, b = 16.5620 (2) ?, c = 5.2240 (1) ? and Z = 2.

Domain Evolution of Herringbone Structures in Ferroelectric Single Crystals

The microstructure of a ferroelectric single crystal is significantly affected by applied loads. Domains evolve through equilibrium states, following a route that minimizes the overall energy. The herringbone pattern is one of the most widely observed domain structures in ferroelectric crystals. In this work, the evolution of four types of herringbone pattern in the tetragonal crystal system is studied by using a variational method. These four herringbone patterns are periodic rank-2 laminates which satisfy compatibility across every domain wall. The unit cell of periodic structure dictates a set of domain walls whose positions may vary while maintaining the same topology. The model allows for a crystal with one type of herringbone domain pattern to switch to another pattern through “pivot states”. In this study, a domain evolution map showing all paths between the four types of rank-2 herringbone pattern and their pivot states is developed. Hysteresis loops such as those observed in ferroelectric single crystals subjected to variety of loads are reproduced.

STRUCTURAL, DIELECTRIC AND TRANSPORT PROPERTIES OF (PbSm)(ZrTi)O3 CERAMICS

The solid solutions of Pb 1-x Sm x( Zr 0.50 Ti 0.50)1-x/4 O 3 (PSZT), x = 0.00, 0.03, 0.06 and 0.09 were prepared by a mixed oxide method at high temperature (sintering temperature 1200°C). Preliminary X-ray structural analysis suggests the formation of single-phase compounds at room temperature in tetragonal crystal system. The microstructural SEM analysis shows that the grains of the materials are almost spherical and also uniformly distributed over the surface. Detailed studies of dielectric properties (ε, tan δ and σ) of the materials in a wide temperature range (30–500°C) at different frequencies (103–106 Hz) reveal that the compounds have transition temperatures well above the room temperature. The analysis of the diffusivity of the dielectric peaks in these compounds provides values between 1 and 2, where the higher values indicate great disorder in the system. The temperature dependence of ac conductivity and the value of activation energy in different regions suggest that the conduction process is of mixed type (i.e. singly ionized in ferroelectric region and doubly ionized in paraelectric phase).

Phase Development during Mixed–Oxide Processing of a [Na0.5K0.5NbO3]1-x -[LiTaO3]x Powder

Powders of the solid solution series [Na0.5K0.5NbO3]1-x - [LiTaO3]x, with x = 0.06, are shown to transform from an orthorhombic to a tetragonal crystal system as calcination temperature is increased in the range 850 °C to 1100 °C. Addition of 3 wt% of each alkali carbonate prior to calcination allows retention of the orthorhombic phase to 1100 oC. The latter changes in phase content are attributed to a partial compensation of alkali oxide volatilisation losses. The approach of adding extra alkali carbonates lead to an increase in d33 coefficient in sintered ceramics.

Formation of iodine-doped C60 whiskers by the use of liquid–liquid interfacial precipitation method

Iodine-doped whiskers of C60 (I–C60 whiskers) with diameters ranging from submicrometers to micrometers and lengths longer than 100 μm were successfully obtained by the use of the liquid–liquid interfacial precipitation method. Transmission electron microscopy observations showed that the I–C60 whiskers were single crystalline and had a growth axis parallel to the close-packed direction of C60 molecules and expanded (002) lattice planes indicative of the intercalation of iodine and oxygen atoms between the (002) planes of a body-centered-tetragonal crystal system. The I–C60 whiskers showed nonlinear I-V curves. The electrical resistivity of the I–C60 whiskers was more than three orders of magnitude lower than that of pristine face-centered-cubic C60 crystals.